The present invention relates to an apparatus and a method for printing images; the invention especially concerns the printer configuration. The invention is particularly suitable for ink-jet printing using a belt for conveying an image receiving substrate.
In many ink jet printers, transport of the image receiving substrate in one or the other stage of the printing process, proceeds by a belt, c.q. a vacuum belt.
E.g. U.S. Pat. No. 4,469,026 discloses a printer having a sheet fed and drum transport assembly. Ink is applied to a sheet while it is transported by the drum. Subsequently, the receiving substrate is detached from the drum and conveyed by a vacuum belt past a dryer.
In U.S. Pat. No. 5,712,672 a printer is disclosed wherein sheets are transported by means of a vacuum belt past an ink-jet printhead and through a microwave dryer.
Patent application WO 99/11551 discloses a printer wherein sheets are transported by a vacuum drum. A simplex printer has one vacuum drum, while a duplex printer uses two counter-rotating drums. In a duplex printer, a first image is printed on one side of a paper sheet while the sheet is on the first drum; then the paper is fed to the second drum so that the first printed image contacts the second drum, and a second image is printed on the opposite side of the paper. The printer can also be used to print on a continuous web instead of on separate sheets.
Printers wherein the image receiving substrate passes the printhead while it is carried by a belt (a vacuum belt as well as a non-vacuum belt) can have problems with keeping the xe2x80x9cthrow distancexe2x80x9dxe2x80x94i.e. the distance that the ink has to travel between the ink application means, for instance an ink-jet nozzle, and the receiving substratexe2x80x94constant while such a belt can show movement to and away from the printhead, vertical movement. It is also possible that, during operation of the printer, such a belt not only shows a vertical movement, but also some lateral movement, so that the registering of colour selection of the image to be printed on the receiving substrate is not as good as it should be.
In U.S. Pat. No. 5,966,145 it is disclosed to support the belt underneath the printhead so as to avoid the movement to and away from the printhead. The support is in sliding contact with the belt and does not add to the tensioning of the belt, so that problems with wear of the belt due to the sliding contact exist and since the supports do not add to the tension of the belt, the problems of vibration sill exist.
Thus it is still desired to have means and ways available to minimise and even totally avoid undesired movement of the vacuum belt, without excessive wear of the belt.
It is an object of the invention to provide an ink jet printer with a belt for transporting an image receiving substrate comprising means for minimising or even avoiding undesired movements of the belt that can deteriorate the image quality of the printed image.
It is a further object of the invention to provide an ink jet printer with a belt for transporting an image receiving substrate comprising means for minimising or even avoiding undesired vertical movement of the belt so as to have a constant xe2x80x9cthrow distancexe2x80x9d.
It is an other object of the invention to provide an ink jet printer with a belt for transporting an image receiving substrate comprising means for minimising or even avoiding lateral movement of the belt so as to have a good registering of colour selections of the image to be printed on the receiving substrate.
The first object of the invention is realised by providing an ink jet printer comprising
an ink ejecting means (11),
a belt (14) for passing a receiving substrate (20) near said ink ejecting means and
a first and a second roller (13, 15) for moving said belt (14) in the sense of arrow A, each of said rollers having a first and a second end and an axis (13a, 15a), characterised in that
said belt (14) contacts a guiding means (18), placed between said first and second roller, for creating a bulge, d, in said belt (14), extending towards said ink ejecting means (11).
The second object of the invention is realised by providing an ink jet printer comprising
an ink ejecting means (11),
a belt (14) for passing a receiving substrate (20) near said ink ejecting means and
a first and a second roller (13, 15) for said moving said belt (14) in the sense of arrow A, each of said rollers having a first and a second end and an axis (13a, 15a), characterised in that
said first roller (13) has flanges (13b) at said first and second end and is placed in said printer so that it deviates from parallelism with said second roller (15).
In a very preferred embodiment of this invention there is provided an ink jet printer comprising
an ink ejecting means (11)
a belt (14) for passing a receiving substrate (20) near said ink ejecting means (11) and
a first and a second roller (13, 15) for said moving said belt (14) in the sense of arrow A, each of said rollers having a first and a second end and an axis (13a, 15a), characterised in that
said first roller (13) has flanges (13b) at said first and second end and is placed in said printer so that it deviates from parallelism with said second roller (15) and
said belt (14) contacts a guiding means (18), placed between said at least two rollers, for creating a bulge, d, in said belt, extending towards said ink ejecting means (11).